52 



AROMATIC COMPOUNDS 



OCH 



OCH 



Phyllodulcin 



Bergenin from rhizomes of Bergenia crassifoUa is an unusual isocoumarin which contains 

 a fused ring apparently derived from glucose: 



CH2OH 



Bergenin 



The coumarins have quite varied physiological effects on living organisms. In some 

 cases they act as plant growth inhibitors, but growth stimulation has also been observed. 

 Coumarins also show narcotic and other toxic effects on animals, but they are generally 

 less toxic than the furanocoumarins (see below). 



Dean (13) has reviewed the naturally occurring coumarins. 



FURANO- AND PYRANOCOUMARINS 



Several natural products are known which have a pyran or furan ring fused with the 

 benzene ring of a coumarin: 



Furanocoumarins 



Pyranocoumarins 



The ring fusion may also be at positions 6 and 7 of the coumarin nucleus. These com- 

 pounds resemble the simple coumarins. Alkaline hydrolysis under ordinary conditions 

 affects only the lactone ring, but alkaline fusion or drastic hydrolysis conditions may 



